In order to test the suitability of a solvent for extraction purposes, 1.250 g of solute with molar mass 132.1 g/mol was dissolved in 10.00 mL of water. 5.00 mL of toluene was added, and the system allowed to equilibrate. After extraction 0.925 g of solute is recovered in the organic phase. What is the partition coefficient between water and toluene (expressed as a log K)?

Question

Quizplus · Accepted Answer

The partition coefficient (K) is calculated as the concentration of solute in the organic phase divided by the concentration in the aqueous phase. After extraction, 0.925 g is in the organic phase, leaving 0.325 g in the aqueous phase. The concentrations are 0.185 g/mL in toluene and 0.0325 g/mL in water. K = 0.185/0.0325 = 5.69. Log K = log(5.69) = 0.76. Therefore, log K = -0.76.

In Order to Test the Suitability of a Solvent for Extraction